You can actually utilize the Linq namespace of the NewtonSoft.Json and modify your code little bit to get only the "popup" elements from the JSON.
your class structure remains the same. Make sure you use the namespace(s)
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
then in your code once you have the JSON string with you, you can use the "JObject" static method "Parse" to parse the JSON, like
var parsedObject = JObject.Parse(jsonString);
This will give you the JObject with which you can access all your JSON Keys just like a Dictionary.
var popupJson = parsedObject["menu"]["popup"].ToString();
This popupJson now has the JSON only for the popup key.
with this you can use the JsonConvert to de- serialize the JSON.
var popupObj = JsonConvert.DeserializeObject<Popup>(popupJson);
this popupObj has only list of menuitems.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…